This invention relates to a document feeding device for feeding originals automatically to an optical scanning position.
In electrophotographic copying, an image of an original is subjected to exposure on a recording medium and changed to a certain polarity, for formation of an electrostatic latent image. The electrostatic latent image so formed is developed with a colorant toner, and the developed image (toner image) is transferred onto a transfer medium (ordinary paper or the like) and fed in suitable manner. The toner image on the transfer medium, being still unfixed as such, is fixed on the transfer medium by the medium being conveyed to a fixing station after image transfer.
In such electrophotographic copying, an original to be copied is placed on a document scan surface. In this case, such document is manually placed on the scan surface. In order to eliminate such manual work, the general practice is to add to the copying machine an automatic document feed device designed so that documents placed on a certain tray are automatically fed one by one for delivery through a conveyor device onto the document scan surface. With such an arrangement it is possible to eliminate such manual work as replacement of an original with a new one upon completion of one copying work, and also to substantially reduce the copying time involved.
Various kinds of improvements have been made with aforesaid automatic document feed device. One recent development is seen in Japanese Published Examined Patent Application No. 59-7102, in which there was proposed a device called "automatic document feeder". This device permits copying of not only single-sided documents, but also double-sided documents. More particularly, the device is such that documents on a loading board (tray) are separated and fed sequentially from the upper most one thereof, each document being taken off after having been delivered onto the scan surface. In this case, documents to be taken off are delivered onto a take-off tray provided separately from the loading tray. Therefore, this device is applicable for use as an ordinary type automatic document feeder, and cannot be employed as a device of such type as is recently known as recirculating document handler. The recirculating document handler is of such arrangement that documents are sequentially fed onto a scan surface and subsequently returned to a document loading board so that they may be again fed onto the scan surface.